Up till now, in 3GPP RAN LTE (Long Term Evolution), studies are underway for single carrier with frequency domain equalization (“SC-FDE”) in the uplink and downlink. In a communication system for performing SC-FDE, to prevent inter-block interference due to multipath, as shown in FIG. 1, a signal is generated by attaching part of the tail end portion of the data block to be transmitted, to the head of that data block as a cyclic prefix (“CP”). Signals generated as above are transmitted from the transmitting side, and the direct waves and delay waves are combined on the channel and arrive at the receiving side. The receiving side performs timing synchronization processing on the received signal, removes the CP part and extracts a signal of one block length from the head of the direct wave block without a CP. The extracted signal is demodulated by performing equalization processing (frequency domain equalization) on the wave distortion in the frequency domain.
To be more specific, in 3GPP RAN LTE, studies are underway for, in the uplink, performing an SC-FDE using the transmission format shown in FIG. 2 (e.g., see Non-Patent Document 1). In the transmission format shown in FIG. 2, one subframe is comprised of two blocks of different block lengths, namely, long blocks (“LBs”) and short blocks (“SBs”). Here, an example case will be explained where one subframe is comprised of six LBs (LB #1 to LB #6) and two SBs (SB #1 and SB #2). The LB length is twice as long as the SB length. Here, data sequences are mapped in LBs and pilot sequences for data demodulation are mapped in SBs. That is, the length of a pilot sequence is the same as the SB length. As shown in FIG. 2, part of the tail end portion of each LB is copied and attached to the head of that LB as a CP. Further, part of the tail end portion of each SB is copied and attached to the head of that SB as a CP.
FIG. 3 illustrates the transmission format shown in FIG. 2 in detail. With FIG. 3, a method of transmitting pilot sequences in the transmission apparatus and a method of calculating channel estimation values for data demodulation based on the pilot sequences in the receiving apparatus, will be explained. As described above, the length of a pilot sequence to be transmitted in the transmitting apparatus is the same as the SB length, and an SB-length pilot sequence is mapped in SB #1 and SB #2 in one subframe. Further, part of the tail end portion of SB #1 and SB #2 is copied and attached to the head of SB #1 and SB #2, as a CP. The SB length is shorter than the LB length (in this case, the LB length is twice as long as the SB length). Consequently, as shown in FIG. 4, upon calculating channel estimation values in the receiving apparatus, the subcarrier intervals in the pilot sequence mapped in the SB (Δf_pilot) are greater than the subcarrier intervals in the data sequence mapped in the LB (Δf_data) (here, Δf_pilot=2×Δf_data). Therefore, the channel estimation value calculated from the subcarrier intervals in the pilot sequence needs to be interpolated in the frequency domain to calculate the channel estimation value associated with the subcarrier intervals of the data sequence.
Non-Patent Document 1: 3GPP TR25.814 V7.0.0 (2006-06)